Isophoric News · Tuesday, October 27, 2026
Researchers in Virginia follow tagged monarchs to Mexico using tiny Bluetooth tags and ordinary phones
Researchers at Virginia Tech's Conservation Management Institute, Jennifer Weber and Shawn Kurtzman, have fitted 35 monarch butterflies with radio-pulse tags weighing less than half a gram and are following them on their fall migration, according to a Virginia Tech release carried by Phys.org. The tags give off a pulse that Bluetooth-enabled phones, vehicles and cell towers can pick up and relay, sending only the tag number and location, so the data come from passersby's devices. Weber said one tagged monarch, Sneezy, was detected in Mexico on Oct. 17, and another, Thomas, was last detected in Mississippi and then about 1,000 miles away in southern Mexico, which she said was probably because a storm system carried him across the Gulf. This is a small, observational tracking project, not a finished study. A monarch flying over open country can go days without a detection, so the researchers cannot tell whether a silent butterfly has lost its tag, died or is simply out of range. The U.S. Fish and Wildlife Service separately described a similar effort with solar Bluetooth tags weighing six milligrams, saying Project Monarch followed 200 monarchs in real time in fall 2025 and that a butterfly tagged in northeast Utah on Sept. 2 was the first radio-tagged monarch it knew of to be detected in Mexico, on Oct. 11 in Santa Catarina, Nuevo León.